You may have seen them making off with a pizza on the subway platform, or taking selfies with sleeping passengers – but the lives of New York City’s notorious rats still largely remain a mystery.

There could be anywhere from 2 to 32 million rats living in the city, but the challenges of safe handling and locating have so far hindered research on these populations.

Now, researchers have proposed a five-step protocol to monitor urban rats and the pathogens they may carry, using microchips and remote sensors to reveal new insight on the behaviours of the ‘ghosts of Gotham.’

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You may have seen them making off with a pizza on the subway platform, or taking selfies with sleeping passengers – but the lives of New York City’s notorious rats still largely remain a mystery. There could be anywhere from 2 to 32 million rats living in the city

RATS IN THE CITY

There could be between 2 and 32 million rats living in New York City.

But, they live underground and often remain unseen.

The researchers say 75 percent of the world's rats will live in urban areas by 2050, raising concerns about the spread of disease.

Rats are known to carry a slew of pathogens, including rat bit fever, Rock Mountain spotted fever, Lyme disease, and cat-scratch disease.

But, researchers say there are likely many more that have yet to be discovered.

In a study published today in the journal Frontiers in Public Health, researchers explain the five-stage protocol that could make for cheaper, safer method of tagging city rats.

Rats are known to carry a slew of pathogens, including rat bit fever, Rock Mountain spotted fever, Lyme disease, and cat-scratch disease.

But, researchers say there are likely many more that have yet to be discovered.

Rats are difficult to handle safely, and they learn to avoid traps, preventing recapture. Along with this, current knowledge relies largely on daylight observations, which are not representative of the population.

‘We don’t know much about the behaviour of city rats, or as much as we need to know about the organisms they can transfer to humans, either directly or indirectly through ticks and fleas,’ says Michael H. Parsons, a researcher at the Department of Biology at Hofstra.

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‘For example, there are currently no known routine surveillance programs for rats in the USA, nor are the population dynamics of rat pathogens systematically monitored in any part of the world.

‘But it’s imperative that we study these subjects because by the year 2050, 75% of the world’s population will live in urban areas, and could therefore be exposed to rat pathogens.

Even today, rats and other rodent pests cost the US an estimated economy of $19 billion per year from food loss, infrastructure damage, and disease.’

The researchers have used this to spot numerous ‘rat catch basins’ in the city, and the continued use of such a method could help to improve our understanding of how they act, and spread disease. Several burrows can be seen above, in a NYC park

The new method, tested on rats in New York City, would provide a new way for researchers to locate rat colonies so they can be trapped and anesthetized to collect samples.

This would include blood, fecal and skin parasite samples.

Then, the rats would be implanted with an RFID microchip, allowing researchers to monitor their daily activity at ‘reading stations,’ where natural rat scents would be used as a lure.

‘We developed the first safe method – not only for researchers, but also for the rats – for collecting pathogens from the same rat individuals over time, while monitoring their individual behaviours and predispositions,’ says Parsons.

‘We show that rats can be effectively monitored with RFID microchips, without a lot of funds – the total cost of our experiment was less than $15,000.’

The researchers have used this to spot numerous ‘rat catch basins’ in the city, and the continued use of such a method could help to improve our understanding of how they act, and spread disease.

When a tagged rat approaches a station, a scale and camera will collect weight and video footage.

So far, this has shown that city rats have a diverse range of personalities and sexual habits.

The researchers recorded some shy rats, and some bold, and say female rats are most sexually active during the day, while males sought sex both day and night.

‘We’re looking forward to seeing others using or improving our protocol, so that rat populations and their pathogens can be systematically monitored to help protect against potential disease outbreaks,’ says Parsons.

‘Even in our home city of New York, with more than 8 million people, there are fewer than 10 institutional researchers pursuing rat research – perhaps we can help change that.’